Flake said he would "immediately draft and introduce legislation to nullify these tariffs," which he called "ill-advised." He said trade wars can only be lost and that Congress "cannot be complicit as the administration courts economic disaster."

Trump signed a 25 percent import tariff on steel and a 10 percent one on aluminum on Thursday, saying it was for both economic and national security.

Republican leaders cautioned Trump against the tariffs, saying they could balloon into a full-scale trade war. And the European Union already signaled it plans to respond with tariffs on American industries.